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Since each VNTR region consists of repeats of a specific sequence of bases, complementary oligonucleotides can be synthesized. These oligonucleotides, when labeled with a marker such as P32 or a chemiluminescent compound, are known as probes.
There are five basic steps to developing DNA profiles using VNTRs:
- Extracting DNA
- Cutting DNA into fragments using restriction enzymes
- Separating the fragments based on size using gel electrophoresis
- Transferring the fragments to a nylon membrane (southern blotting), causing immobilization
- Locating and identifying the fragments by applying a solution containing the probe of interest, which then hybridizes to the immobilized DNA. Visualization of the fragments requires a lengthy exposure of the probe to a detection system and can add several days to the assay time.
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